G1i: Anatomy of the heart, including valves, chambers and the pericardium
- The heart is a muscular pump which propels blood to all parts of the body
- Heart consists of 3 layers:
- Endocardium: thin internal epithelial layer
- Myocardium: thick middle layer of cardiac muscle
- Epicardium: thin external layer formed by visceral layer of pericardium
Fibrous Skeleton of Heart
- Dense framework of collagen
- Surrounds valve orifices
- Anchors muscle fibres
- Provides attachments for valves
- Electrical insulation separating atrial & ventricular syncytium
Atria
- Structure – thin walled, low P chambers
- Coronary sinus opens into RA between AV orifice & IVC orifice
- Four pulm. veins open into LA posterior wall
- Function – reservoir. Adds 30% to ventricular filling
Ventricles
• Right Ventricle
- Thin walled 2° lower pressure operation
- Chordae tendinae connect AV valves to papillary muscles of ventricles
• Left Ventricle
- Twice as thick cf. RV, does most of work
- Larger papillary muscles → work harder
• Function
- Papillary m. & chordae tendinae prevent bulging of AV valves into atra during systole
- Ventricles propel blood towards outflow tract
Valves
• Structure
- Endothelium covered in fibrous tissue
- Firmly attached to fibrous rings of cardiac skeleton
• AV valves
- Tricuspid & mitral valve
• SL valves
- & aortic have 3 cusps
- Behind valves are small outpockets k.a. Sinuses of Valsalva
- Orifices of RCA & LCA are behind R & L cusps of Aorta
• Function
- Unidirectional flow of blood through heart
Pericardium
• Structure
- Double walled fibrous sac
- Enclosing heart & great vessels
• Function
- Lubrication for continuous contraction by pericardial fluid
- Minimal distensibility → resists large & rapid ↑ cardiac size
→ keeps Starling curve on steep portion